The present invention relates to a fine particle sensor for detecting fine particles (e.g. soot) in exhaust gas and a mounting structure for mounting a fine particle sensor to an exhaust pipe of an internal combustion engine.
In the following description, the terms “front” and “rear” are used with respect to the axial direction of a fine particle sensor and, more specifically, the direction of insertion of the fine particle sensor into an exhaust pipe; and the terms “upstream” and “downstream” are used with reference to the direction of gas flow in the fine particle sensor or in the exhaust pipe.
Fine particles (e.g. soot) are contained in exhaust gases of internal combustion engines (such as diesel engines and gasoline engines). It is thus common practice to mount a fine particle sensor on an exhaust pipe of the internal combustion engine in order to detect the amount of fine particles in the exhaust gas and limit the amount of fine particles discharged to the atmosphere as disclosed in Japanese Translation of PCT International Application Publication No. JP-T-2007-514923 and PCT International Application Publication No. WO2009/109688. However, there is a problem that the detection accuracy of the conventional fine particle sensor tends to vary depending on the flow of the exhaust gas in the exhaust pipe.